Unable to resolve superclass error when referencing .jar library

1. I did an Android project and run it. It ran successfully.
2. I developed a web service in Java and hosted it. It ran succe开发者_JAVA百科ssfully.
3. I exported the webservice into a .jar and added it to my Android project.
4. When I try to call a method in the web service I get an Unable to resolve superclass error.

My error log:

Unable to resolve superclass of Lweb/service/RandomWordGeneratorService; (73)
Link of class 'Lweb/service/RandomWordGeneratorService;' failed 
Could not find class 'web.service.RandomWordGeneratorService',
    referenced from method tam.miru.Login$1.onClick
VFY: unable to resolve new-instance 110 Lweb/service/RandomWordGeneratorService;)
    in Ltam/miru/Login$1; 
VFY: replacing opcode 0x22 at 0x005a    
VFY: dead code 0x005c-006e in Ltam/miru/Login$1;.onClick (Landroid/view/View;)

Just started to get this issue after upgrading to ADT 17.

Discovered that external .jar files need to be in a 'libs' (with an s) folder otherwise their classes are not included in the .dex file that is created. Before the upgrade everything worked fine with my .jar files in a 'lib' folder (no s).

In my case I had to go to Properties->Java Build Path->Order and Export and check Android Private Libraries, then cleaned the project and worked fine.

Create lib folder, libs folder is for native libraries. I made it, add library to lib and to build path as internal library and it works!

Are you using eclipse? If so, did you add the library to the build path as described in Adding a library/JAR to an Eclipse Android project?

I know that this a post on a really old thread, but after I read the answer by @rabidgremlin, I checked the folder structure, and found that it was already in "libs". However, on seeing the support.jar, I figured that using this was what was causing the issue.

I was extending "FragmentActivity" but it turns out, that was referencing the support.jar, which had issues in itself. Once I removed the extends clause, the app miraculously stopped crashing.

Just an FYI in case someone comes looking. Cheers!

I had the same problem, I tried to mark the Android Private Libraries under Order and Export and it didn't work for me. Then I noticed that my libs folder wasn't referenced under the Java Build Path. So I just added it to Libraries and it worked.

I had the same error message. Took me some time to figure out the problem: Android requires Java 1.6 to work. And the superclass of my Activity implemented an interface from a Java project that had Java 1.7 as compiler. That was enough for the dex builder not to be able to link the superclass and this resulted in the class not found exception.

I ran into a different cause for this error on Eclipse. I was experimenting with putting eclipse workspaces into google drive directories and discovered that certain superclasses can't be resolved from android activities.

Paused google drive and everything began working fine. In my case the superclass that wouldn't load was from a protocol buffers generated class. This class and all others I tested worked fine in non-android java programs, even while google drive was running.